Abstract
Based on the direct numerical simulation (DNS) data, the generation mechanisms of hairpin vortices are studied in the research. The momentum thickness Reynolds number range is 250 < Reθ < 438. It is found that the hairpin vortex can be evolved from a spanwise vortex. A new hairpin vortex can also be formed from a pair of streamwise vortices. Besides, a younger hairpin vortex may be generated from the primary hairpin vortex. Apart from these three ways, a new hairpin vortex can be evolved from a pair of separated arch-shaped vortices, referred to as the fourth way. It is the first time that direct evidences are found for this particular generation process of hairpin vortex. The convincing proofs are shown by the Liutex iso-surfaces and LXC-liutex core line methods. The inherent mechanism of this phenomenon is analyzed and explained by the Biot-Savart law. It is concluded that the new hairpin evolves from a pair of arch-shaped vortices when the pair of arch-shaped vortices move downstream side by side in a short distance.
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Li, H., Wang, D., Xu, H. (2021). Hairpin Vortex Formation Mechanisms Based on LXC-Liutex Core Line Method. In: Liu, C., Wang, Y. (eds) Liutex and Third Generation of Vortex Definition and Identification. Springer, Cham. https://doi.org/10.1007/978-3-030-70217-5_12
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DOI: https://doi.org/10.1007/978-3-030-70217-5_12
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